The present invention relates in general to a variable electronic component, and more particularly, to a sealed, variable trimmer capacitor adapted to provide a high resolution operative range of impedance characteristics employing a pair of free-floating dielectric plates.
In the advancing technologies of computers, testing equipment, appliances and other fields, various types of hybrid electronic circuits, integrated electronic circuits, micro strip amplifiers, micro electronic systems and other electronic devices are being developed and which are being made on increasingly smaller scale and size than has been known heretofore. In accomplishing this end, these devices are generally mounted on small flat insulating bases known as substrates. These various devices incorporate or have formed therein or co-act with various types of electronic components such as inductors, capacitors, resistors, potentiometers, etc., which in turn must be as small as possible to meet the demands of the reduced scale or size of these devices.
The known miniature devices have reached their functional limit even with the best precision manufacturing techniques because certain elements of these devices cannot be reduced further at reasonable cost for commercially acceptable regularly usable devices. U.S. Pat. Nos. 3,679,940 and 3,757,266, which patents are assigned to the same assignee of the within invention, each disclose variable electronic components, such as capacitors and resistors, which are particularly adapted to meet and overcome the problems of these known devices by eliminating the area and mass of conventional mounting frames, tuning mechanisms and other elements heretofore used, and instead integrate the elements of these variable electronic components directly into the circuit. These components are primarily designed as low-profile structures exceedingly small in size, simple in construction, easily adjustable, reliable in operation, easily replaceable and reproducible in quantity without sacrificing uniformity or performance. However, these variable electronic components are not sealed within a housing, thus subjecting their elements to processing fluids used during the manufacture of the electronic circuits into which they are incorporated. Another variable capacitor of the very low resolution type, i.e., one-half turn resolution, and which is also unsealed is known from U.S. Pat. No. 3,701,932.
Owing to the exceedingly small size of these variable electronic components, the ability to provide a high resolution device and to readily adjust these components have likewise become exceedingly more difficult. These low resolution devices have been provided with an upturned tab to be engaged by a suitable adjustable tool, for example, a tweezer, so as to effect the desired operative range of impedance characteristics of the component. As these components become increasingly smaller in size, it can be appreciated that there is a need to provide a more accurate and reliable means of providing the requisite adjustment, as well as in providing their resolution. There has been known to include in these variable electronic components a rack and pinion assembly operable upon rotation by a miniature screw driver in order to facilitate their adjustment.
One variable electronic component which satisfies the aforementioned objective is known from U.S. Pat. No. 4,575,779, which patent is assigned to the same assignee of the within invention. This known variable electronic component is constructed specifically as a low resolution device to include an eccentric whose rotational motion imparts reciprocal movement to an impedance-varying member. The eccentric is operative by engagement with an implement such as a screw driver and the like. However, the elements of this variable electronic component are not contained within a sealed housing, and are therefore exposed to the environment which can effect the component's impedance characteristics due to corrosion and other such action over time.
One variable electronic component which is contained within a sealed housing is known from U.S. Pat. No. 4,876,627, which patent is assigned to the same assignee of the within invention. This known variable electronic component includes within the sealed housing a cylindrical rotor having an impedance varying portion in cooperative association with a dielectric plate to provide the desired range of impedance characteristics. The rotor includes a plurality of circumscribing teeth extending radially outward in meshed engagement with the threads of a rotatable worm gear. This design of the variable electronic component has proven difficult to manufacture due to difficulties resulting from the relatively small size of these components and their associated threads which require a certain degree of design tolerance during molding from plastic material to ensure accurate operation of the variable electronic component over its capacitance range.
Accordingly, it can be appreciated that there is an unsolved need for a sealed variable electronic component, such as a variable trimmer capacitor, which can provide a desired high resolution operative range of impedance characteristics quickly, simply and inexpensively by adjustment using a suitable implement such as a screw driver and the like.